1. Field of the Invention
This invention relates to a tube assembly with a breakaway plug. More particularly, it relates to a tube assembly having a breakaway plug which is unlikely to be ruptured or contaminated before use.
2. Discussion of Prior Art
In some branch tubes such as four-way branch tubes for use in combination with blood collection bags, all the branches are not used at the same time, but they are used one by one in successive steps. To prevent the flow path from being contaminated from a branch which is not in use, the branch not in use should be completely sealed with a plug or a suitable closure. Upon use of the branch which has been sealed with a plug, it is necessary that the plug be readily broken and removed to open the associated branch to allow for connection to another member such as a tube having a puncture needle.
A variety of plugs which can be torn off have been proposed in the prior art. For example, T. Gewecke, U.S. Pat. No. 3,368,560 discloses an outlet fitting wherein a cap portion is united to a tubular portion by means of a relatively thin annular web. A finger tab depending from the cap portion is pulled whereupon a line of severance occurs in the area of the integral web.
This fitting is applicable as a plug on a branch of a four-way branch tube, but has a problem in operation. When the cap is pulled with a considerable force in an axial direction to cut the cap at the thin web, there occurs an impact of reaction At the instant of rupture, the operator would probably hit something at her elbow. Additionally, the cut edge would be brought in contact with something so that it might be contaminated.
C. Robinson et al, U.S. Pat. No. 4,228,835 discloses a breakaway cap comprising a ring having an open end and a closed end with a handle An annular grooved area is provided as a frangible connection between the open end portion and the closed end of the ring. When the handle is grasped and moved angularly, the ring will break at the frangible section to remove the handle from the ring. The cap is formed of a polyvinyl chloride having a hardness in the range of 85-100 as measured on the Shore A scale of a durometer.
This cap is also applicable as a plug on a branch of a four-way branch tube and considered as preventing the inadvertent reaction of breakage inevitable with the cap of Gewecke. The cap has a certain degree of hardness so that it is broken at the frangible section by moving the handle angularly. Since the plug or breakaway cap is united with the frangible section and a flexible tube is connected to the ring portion of the cap left after breakage, the ring portion of the cap must be utilized as a waist in bending the handle. For this reason, the cap is made of a material having a Shore A hardness of 85-100. Since the cap of this range of hardness is rather less flexible, it has problems in gas tightness, adherence to the branch or tubular body, and prevention of accidental rupture before it is desired to break the plug to open the flow path of the branch on use.